The invention relates to a multi-pin (terminal for external connection) semiconductor device with an integrated circuit mounted therein, for processing several signals including RF signals, and more specifically, to a semiconductor device wherein pads (electrodes) provided on a semiconductor chip (semiconductor piece) are connected with terminals (terminals for external connection) on the side of a package so as to correspond to each other, respectively, by a bonding wire (thin metal wire), respectively.
With a semiconductor device for processing RF signals, by, for example, directly connecting ground leads juxtaposed with signal leads to the back surface of a semiconductor chip, and further, by providing even a metal sheet in parallel with ground electrodes, grounding impedance at a resonance frequency is rendered zero in order to reduce undesirable reflection at input/output terminals (JP, H8-237001, A). Since such a semiconductor device for RF is generally not highly integrated, and is provided as a single-function item/a special-purpose item, for processing a single or a few signals, pads (electrodes) on the semiconductor chip and terminals for external connection on the side of a package are only a few in number.
On the other hand, with a semiconductor device that does not handle signals at so much high frequencies, but exchanges a large number of signals with the outside, advances have since been made towards multiplication of pins along with higher integration, so that the number of bonding pads as well as bonding wires has increased.
Shown in FIG. 7 as an example of such a semiconductor device is an IC1, which is obtained by packaging a semiconductor chip (semiconductor piece) 2 with a plastic mold 1a, and a multitude of terminals (terminals for external connection) 1b are also assembled therein in such a way as to be partially exposed. On the central part of the main top surface of the chip 2, there is formed a signal processing circuit (integrated circuit) 2a, on the periphery of which there are formed signal input circuits and signal output circuits (integrated circuits) 2b. On the outermost peripheral parts (peripheral edge parts) of the signal processing circuit 2a, there are formed bonding pads (electrodes) 2c so as to be juxtaposed at predetermined pitches.
Any one (power source electrode) among a multitude of the bonding pads 2c is connected with power source lines of the signal processing circuit 2a, the signal output circuits 2b, etc. via a patterned wiring layer etc., formed in the chip 2, respectively, and at the same time, is connected with a terminal 1b (Vcc) for power source voltage application via a relevant bonding wire 3. Further, another bonding pad (reference electrode) 2c is connected with reference voltage lines of the signal processing circuit 2a, the signal output circuits 2b, etc. via a patterned wiring layer etc., formed in the chip 2, respectively, and at the same time, is connected with a grounding terminal 1b (GND) via another relevant bonding wire 3. Remaining bonding pads (signal electrodes) 2c are connected with relevant signal lines of the signal processing circuit 2a, respectively, either indirectly through the intermediary of relevant signal output circuits 2b or directly, and at the same time, are connected with relevant signal terminals 1b (Sig), respectively.
With the multi-pin IC1, the number of the bonding pads 2c formed on the chip 2 is large and in addition, the chip 2 of high circuit integration is so small as to be encapsulated in the plastic mold la while the terminals 1b which are substantially the same in number as the bonding pads 2c are disposed in the surface location of the plastic mold 1a, and in addition, are lined up so as to fit an external mounting condition, so that the pitches at which the bonding pads 2c are juxtaposed are narrower than those for the terminals 1b, and consequently, the bonding wires 3 are provided radially.
Now, with a fast digital signal processing circuit used in an LDVS (Laser Video Disc System) etc., an RF signal processing circuit used in a wireless LAN (local Area Network) etc., and so forth, the above-described ICs of different types are used selectively or in combination.
In the years ahead of the present situation where advances are being made concurrently towards higher-function, higher-speed, and miniaturization, future demands can be foreseen such that the number of semiconductor chips should be held down while the total number of signals to be processed and the number of RF signals contained in the signals are to be increased.
With the conventional semiconductor device described above, however, all the circuits cannot be formed simply in one chip because of difference in conditions for improving frequency characteristics, conditions concerning bonding spots, and so forth.
Accordingly, in forming an integrated circuit for processing a large number of signals including RF signals in one chip, there is encountered a technical problem to devise some effective means for preventing deterioration of RF signals, in particular, the frequency characteristic thereof, while meeting conditions for connecting bonding pads (electrodes) with pins (terminals for external connection), associated with a multi-pin IC, and other conditions.
The Invention has been developed to resolve the problem described, and it is an object of the invention to provide a semiconductor device capable of properly processing RF signals even though the number of electrodes as well as terminals for external connection is large, and pitches at which the electrodes are juxtaposed are narrower than the pitches at which the terminals for external connection are juxtaposed.
With reference to first to fifth problem-solving means according to the invention developed to resolve the problem described above, configurations and operation effects thereof are described hereinafter.
A semiconductor device according to a first problem-solving means is a semiconductor device comprising a semiconductor piece with an integrated circuit for processing signals, formed therein, signal electrodes connected with signal lines of the integrated circuit formed in the semiconductor piece, respectively, a reference electrode connected with a reference voltage line of the integrated circuit formed in the semiconductor piece, a package encapsulating the semiconductor piece, terminals for external connection, juxtaposed on the package at pitches wider than a distance between the respective signal electrodes and the reference electrode adjacent thereto, and a plurality of thin metal wires provided within the package, any thereof connecting any of the terminals for external connection to the respective signal electrodes while any other thereof connecting any other of the terminals for external connection to the reference electrode, wherein the reference electrode is increased in number to plurality, and each of the reference electrodes is disposed on top of the semiconductor piece, and on opposite sides of the respective signal electrodes while short-circuiting means, such as a conductor layer, so forth, for short-circuiting the reference electrodes with each other. on top of the semiconductor piece are provided on the semiconductor piece.
With the semiconductor device according to the first problem-solving means, the reference electrodes short-circuited with each other, and the thin metal wire as well as the terminal for external connection that are connected thereto, are disposed on opposite sides of the signal electrode to which RF signals are transmitted, and the thin metal wire as well as the terminal for external connection that are connected thereto, so that a transmission path for RF signals can be disposed definitely away from a transmission path for other signals, and in addition, current paths for not only direct transmission current for RF signals but also return current in the reverse direction become definite. As a result, noises of either a normal mode or a common mode can be held in check.
Notwithstanding the above, since the characteristic of a multi-pin IC such that the pitches at which the electrodes are juxtaposed are narrower than the pitches at which the terminals for external connection are juxtaposed, a multitude of the electrodes and the terminals for external connection can be ensured even if the semiconductor piece and the package remain small in size, so that a multitude of other signals can be inputted and outputted in parallel and independently. It follows therefore that a multi-function integrated circuit for handling a multitude of signals and a circuit for handling RF signals can be mounted on one chip without impairing the function and performance of either of the circuits.
Accordingly, the invention can provide a semiconductor device capable of properly processing RF signals with the pitches at which the electrodes are juxtaposed remaining narrower than the pitches at which the terminals for external connection are juxtaposed.
A semiconductor device according to a second problem-solving means is a semiconductor device that is the same as the semiconductor device according to the first problem-solving means except that the position of the respective signal electrodes is deviated from the alignment of the reference electrodes. That is, assuming a straight line interconnecting the reference electrodes positioned on respective sides of the respective signal electrodes, the respective signal electrodes are provided at a spot deviated from the phantom straight line.
With the semiconductor device according to the second problem-solving means, either one or both of the signal electrode and the reference electrode in a location where RF signals are transmitted are deviated off an alignment of a multitude of the electrodes including electrodes other than those, within a range where wire bonding can be effected. Consequently, the alignment of the electrodes is somewhat in disarray in the location, however, ignoring such disarray, the fundamental pitches in the direction of the alignment are maintained substantially at the same interval as before on the whole, and yet a distance between the electrodes in the location becomes wider than the respective fundamental pitches in the direction of the alignment.
As a result, there occurs easing of a sudden change in capacitance distributed between the thin metal wires forming a pair, that is, parasitic capacitance distributed between the thin metal wire from the signal electrode to the terminal for external connection, and the thin metal wire from the reference electrode to the terminal for external connection, so that impedance matching can be obtained more properly. Consequently, even if the thin metal wires are in radial shape, resultant undesirable effects on RF signals can be checked.
Accordingly, the invention can provide a semiconductor device capable of more properly processing RF signals with the pitches at which the electrodes are juxtaposed remaining narrower than the pitches at which the terminals for external connection are juxtaposed.
A semiconductor device according to a third problem-solving means is a semiconductor device that is the same as the semiconductor device according to the second problem-solving means except that a conductor layer is extended from the respective reference electrodes or spots where the respective reference electrodes are short-circuited with each other towards both sides of the respective signal electrodes.
With the semiconductor device according to the third problem-solving means, even though the reference electrodes are deviated from the respective signal electrodes, portions of the conductor layer, extended from the reference electrodes, come back to both sides of the relevant signal electrode, so that the relevant signal electrode still remain interposed between extensions of the reference electrodes.
Consequently, even though the respective signal electrodes are deviated from an alignment of the reference electrodes, an electrically separated state of the relevant signal electrode from other signal electrodes is maintained with certainty by the relevant reference electrodes, and the extensions thereof. Furthermore, the extensions, namely, the conductor layer can be easily formed by utilizing a patterned wiring layer, and so forth.
Accordingly, the invention can provide a semiconductor. device capable of more properly processing RF signals with the pitches at which the electrodes are juxtaposed remaining narrower than the pitches at which the terminals for external connection are juxtaposed.
A semiconductor device according to a fourth problem-solving means is a semiconductor device that is the same as the semiconductor device according to any one of the first to third problem-solving means except that a tapered conductor is provided so as to be disposed away from the semiconductor piece, and the extremity of the tapered conductor is positioned closer to the thin metal wire connected with the signal electrode, among the thin metal wires, while the base edge of the tapered conductor is positioned farther from the thin metal wire than the extremity of the tapered conductor, being indirectly connected with the reference electrode.
With the semiconductor device according to the fourth problem-solving means, the extremity of the tapered conductor at the same potential as that of the reference electrode, is positioned in the vicinity of the signal electrode and the thin metal wire connected thereto in the location where RF signals are transmitted.
Parasitic capacitance distributed between the tapered conductor and a thin metal wire from the signal electrode to the terminal for external connection is canceled out by parasitic capacitance distributed between the thin metal wire, and a thin metal wire from the reference electrode to the terminal for external connection, so that a sudden change in impedance distribution can be eased.
Consequently, even if the thin metal wires are in radial shape, resultant undesirable effects on RF signals can be checked.
Accordingly, the invention can provide a semiconductor device capable of more properly processing RF signals with the pitches at which the electrodes are juxtaposed remaining narrower than the pitches at which the terminals for external connection are juxtaposed.
A semiconductor device according to a fifth problem-solving means is a semiconductor device that is the same as the semiconductor device according to any one of the first to fourth problem-solving means except that dielectric constant of a packaging material filling up between the signal electrodes and the terminals for external connection, connected thereto by the thin metal wire, respectively, is variable continuously or in stages along the direction of the thin metal wire, that is, between the respective signal electrodes and the respective terminals for external connection.
With the semiconductor device according to the fifth problem-solving means, in a location where a distance is narrow between the thin metal wire from the respective signal electrodes to the respective terminals for external connection, and the thin metal wire from the respective reference electrodes to the respective terminals for external connection, the dielectric constant of the packaging material is rendered smaller while in a location where the distance between those thin metal wires is wide, the dielectric constant of the packaging material is rendered larger.
Consequently, variation in distribution of parasitic capacitance distributed between the thin metal wires is rendered milder in comparison with variation in distance between the thin metal wires.
Accordingly, the invention can provide a semiconductor device capable of more properly processing RF signals with the pitches at which the electrodes are juxtaposed remaining narrower than the pitches at which the terminals for external connection are juxtaposed.